This invention relates generally to rotary machines and more particularly, to methods and apparatus for monitoring turbine generators.
Many known hydroelectric turbines include a multiple-bladed rotor mounted within a housing coupled in flow communication with an elevated fluid source, such as a reservoir. Water from the source enters a pipe and travels downhill to the hydroelectric turbine. As the water descends, gravitational potential energy is transformed into kinetic energy in the form of mechanical hydraulic energy. The water is then channeled through the turbine wherein it imparts rotation within the turbine. At least one generator rotor is rotationally coupled to, and driven by the turbine rotor. Some known electric generators typically use a plurality of magnets coupled to a rotor and a plurality of stationary wire coils coupled to a stator to convert the turbine's rotational energy into electric energy.
In some known generators, rotor components and stator components are separated by an air gap that is typically measured in distance units. During operation, a magnetic field generated by the magnets mounted to the rotor passes through a portion of the air gap defined between at least a portion of a surface of the rotor and at least a portion of a surface of the stator. The effectiveness of the transmission of the magnetic field through the air gap is at least partly dependent on maintaining the dimensions of the air gap, i.e., the radial distance between the rotor surface and the stator surface. However, asymmetric and/or transient loads induced to the rotor may cause the rotor to deflect such that the air gap dimension is reduced and/or altered to be non-uniform. The changes to the dimensions of the air gap may adversely affect the magnetic field. Moreover, in the event of a generator malfunction, for example, short circuited windings, the effect on the magnetic field may also be adverse.